Fish Aggression Linked to Tank Size Featured

If you are having an aggression problem with the fish in your aquarium, the problem may be that your problem is really overcrowding which increases territoriality and aggression.

Perhaps you already understand the dangers of keeping your fish in a tank that is too small. Many inexperienced aquarium hobbyists, however, do not realize that tank size is an important factor in keeping their fish happy and healthy. If you think about it, small tanks seem to be the norm for certain species like goldfish and betta fish – this simply perpetuates the myth that fish can not only live, but thrive in small tanks.

Basics of Fish Aggression

Though fish may be able to survive in a tank that provides them with limited space, it will not necessarily be a happy life. You may already be aware of the dangers of overcrowding a tank – not only can this lead to problems with water quality and waste accumulation, but it can also exacerbate issues of territoriality and aggression. Numerous studies have shown that even some of the most placid species can display signs of aggression when kept in a tank that is too small. For aquarium fish, signs of aggression may include chasing other fish around the tank, nipping at fins or actually attacking another fish. These issues are most commonly seen in tanks housing numerous males of a single species, but some species are simply more aggressive or territorial than others. A recent study conducted by Dr. Oldfield of Case Western Reserve University revealed that tank size has a significant impact on the display of aggressive behaviors in aquarium fish.

Study by Dr. Oldfield

A biology professor at Case Western, Dr. Oldfield set out to make a connection between aquarium fish behavior and tank size. Previous studies showed that overcrowded tanks often exacerbated behavior problems and decreasing tank size led to an increase in aggression. Dr. Oldfield’s study was among the first, however, to study the effect of increasing tank size on fish behavior. In preparation for his study, Dr. Oldfield studied some statistics on the aquarium hobby in America. Statistics revealed that nearly 13 million Americans own at least one fish tank and, of those tanks, the average size was less than 10 gallons. Tanks of this size are frequently recommended for betta fish and for nano tanks but, unfortunately, many undereducated hobbyists keep fish that are too large for their tanks.

Cichlid fish tank

As part of his study, Dr. Oldfield observed the behaviors of fish when they were put in tanks of increasing size. In order to avoid observations of feeding aggression, his observations were made 2 hours after feeding time. In tanks up to 100 gallons in capacity, aggressive behaviors remained consistent – this remained true regardless how many fish Dr. Oldfield put in the tank. Once the 100-gallon tank capacity was breached, however, something interesting happened – aggressive behaviors dropped off considerably. Dr. Oldfield made a connection using cichlids in their natural habitat as an example. Cichlids living in the Amazon River and other bodies of water, for example, are rarely aggressive at all. Dr. Oldfield attributes this to the fact that they have so much space.

Other Tips for Reducing Aggression

Not only do you need to provide your fish with adequate space to swim and grow, you also need to make sure that the tank is a clean and healthy environment. In addition to performing routine water changes and replacing your aquarium filter media, there is a simple trick you can employ to keep your tank water clean – installing an EcoBio-Stone in your tank. EcoBio-Stones are made from naturally porous volcanic rock and they are infused with live beneficial bacteria. Once installed in your aquarium, these bacteria multiply to establish and maintain the nitrogen cycle in your tank, a key element in cultivating a healthy ecosystem. An EcoBio-Stone lasts for years and it helps to keep your tank water clean, clear and free of odor. Another option is to add some EcoBio-Pebbles to your filter media. These pebbles perform the same duty as EcoBio-Stones and they are particularly recommended for canister filters and other filters that have multiple filter media compartments.